Chips used in radio frequency identifications (RFIDs), electronic article surveillance (EAS) tags, EAS sensors, etc. are generally manufactured by a low cost printing process.
Channel layers that are formed by a printing process include organic semiconductor layers. However, organic semiconductor materials may have low charge mobility and, consequently, it may be difficult to manufacture a high quality transistor using organic semiconductor materials. Thus, transistors having channel layers that include semiconductor oxides have been developed because semiconductor oxides may have high charge mobility.
A channel layer made from a semiconductor oxide generally has one conductivity type because a semiconductor oxide layer that has more than one conductivity type may be unstable. Additionally, forming a channel layer that has two conductivity types using a semiconductor oxide may require an expensive apparatus and/or a complicated manufacturing process. Thus, it may be difficult to manufacture a transistor that has a channel region and a source/drain region which have different conductivity types using a semiconductor oxide.
Accordingly, a source/drain region in a transistor having a semiconductor oxide channel layer may be formed using a metal. The transistor may be a majority carrier device in which a channel layer and charge carriers have the same conductive type. The majority carrier transistor may be mainly operated in an accumulation mode.
A minority carrier transistor may use an inversion layer that serves as a channel layer. This inversion layer may be very thin, e.g., about 3 nm. In contrast, the majority carrier transistor may use fully a three-dimensional volume layer as the channel layer.
In the majority carrier transistor, a carrier flow may be generated not only at a portion of the channel layer adjacent to a gate insulation layer but also at a portion of the channel layer adjacent a passivation layer that protects the channel layer. The passivation layer may include positive fixed charges, which have substantially the same effect as impurities that are doped in the channel layer. Thus, the carrier flow may be increased at the portion of the channel layer that is adjacent the passivation layer, which may deteriorate the ability to control carriers using a gate electrode.